The present invention relates to a monitor and alarm system for a central refrigeration installation for refrigerated display cases.
In commercial refrigeration installations for supermarkets where a number of refrigerated display cases are employed, typically a plurality of refrigerant compressors are utilized to supply high pressure liquid refrigerant to the evaporators contained in the display cases. Typically, a bank of such compressors will be coupled in parallel between a common input refrigerant manifold and an output manifold which, in turn, is coupled to a receiver containing a mechanical refrigerant liquid level sensor. The evaporators of each refrigerated display case are then commonly coupled to the refrigerant receiver and the outputs of the evaporators return to input manifold completing the refrigerant flow path.
In the past, a mechanical dial-type refrigerant level float was mounted to the receiver to provide a local visual indication of the liquid level. Also, a separate fixed alarm switch, set for approximately 20% of liquid level, was provided to provide an alarm output signal at the fixed level for activating a suitable alarm to the system operator. Systems also typically include oil failure sensing switches at each compressor for detecting the oil level contained in each compressor and a remote panel indicating oil level failures as well as monitoring other functions such as suction and discharge pressures at the input and output manifolds, respectively, and a voltage sensor to detect the loss of any one of the three phase input power employed for powering the compressors.
Thus, although some form of monitoring was provided for some conditions in such a system, the known prior art does not provide an integrated monitoring and alarm system whereby a central panel is provided to display all of the monitored fault functions as well as provide, in addition to the alarm indications, a display of the actual refrigerant level.